1. Field of the Invention
The present invention relates to building roof assemblies for building structures, and more particularly, but not by way of limitation, of overroofing preexisting roofs using free roof assemblies.
2. Discussion of Prior Art
Numerous types of reroofing procedures have heretofore been proposed for reroofing preexisting buildings in an effort to provide a watertight, durable roof. It has been understood that the most economical, effective means of accomplishing this is to leave the preexisting roof in place and support the new roof from the preexisting roof or structure. Doing this minimizes the exposure of the contents of the existing structure to the elements during the reroofing process and requires less work and labor to complete the job. More recently it has been recognized that there are significant benefits to sloping the roof so as to drain the water from the roof to eliminate the adverse effects of standing water, such as roof deterioration and potential structural failure. Furthermore, the adverse effects resulting as a consequence of roof expansion and contraction have been recognized.
Typical of such prior art assemblies which have met with some success in recent years are built-up roofs; single-ply roofs; field-applied foam which utilizes an elastomeric top coat in combination with the foam; and other similar systems. These systems have certain disadvantages such as it is difficult to modify the slope of the preexisting roof to achieve suitable roof drainage, the expansion and contraction characteristics of the preexisting roof must often be overcome; and if the preexisting roof has deteriorated to any significant extent, suitable support to resist both inward and outward loads is difficult to achieve.
In very recent times, it has come to be recognized that the metal roof can be employed very advantageously for overroofing preexisting substantially flat sections of preexisting roofs. Furthermore, it is recognized that in many situations multiple flat segments located at different elevations on preexisting roofs can be overroofed using a single sloped metal roof advantageously.
In these applications, the panel members of the standing seam metal roofs are joined to each other along adjacent sides or ends such that these sides and ends are lapped together to form a larger layer roof. These roofs have, in the past, been attached to their supporting structure by either non-penetrating clips or through fasteners and supported by relatively rigid secondary structural members. The attachment of the roof to the relatively rigid secondary structural member, if accomplished by a through fastener, has often resulted in poor roof performance because as the roof expands and contracts the fastener attaching the roof to the underlying structure is apt to rip holes in the roof allowing water to penetrate the roof. On the other hand, if non-penetrating clips which contain sliding mechanisms within the clips are used the problem of roof expansion and contraction is overcome at the expense of assembling and using a complex mechanism, i.e. a floating clip. It has been recognized for some time that the metal roof exhibits considerable diaphragm strength. However, with the employment of floating clips between the support mechanism and the new roof, it has been difficult to take advantage of this inherent strength.